The invention relates to a transverse flux machine comprising a stator with essentially U-shaped and I-shaped cores of a soft-magnetic material and respectively one stator winding for each phase that generates a magnetic flux in these cores, as well as a rotor with a circular magnetic return path, and wherein the stator phases are magnetically separated.
A machine of this type is described in German Patent 196 14 862 A1. The machine consists of a stationary stator and a rotating rotor with permanent magnets, which are mounted on circular soft-iron magnetic return paths. The machine has a multi-phase design, wherein each phase can be viewed as a single-phase machine. A multi-phase arrangement can be obtained by stringing together several phases, wherein each phase is nevertheless insulated magnetically and electrically from the other phases. Transverse flux machines of this type, however, are very expensive to produce because of the permanent magnets and have a relatively low output factor.
It is the object of the present invention to create a multi-phase transverse flux machine, comprising a stator with essentially U-shaped and I-shaped cores of a soft-magnetic material and respectively one stator coil for each phase that generates a magnetic flux in these cores, as well as a rotor with circular magnetic return path, wherein the phases of the stator are magnetically separated. The machine should be cheap to produce and should have a relatively high degree of efficiency.
The above object generally is achieved according to the invention by a multi-phase transverse flux machine, comprising a stator with essentially U-shaped and I-shaped cores of a soft-magnetic material and respectively one stator winding for each phase that generates a magnetic flux in these cores, as well as a rotor with a circular magnetic return path; and wherein: the stator phases are magnetically separated; the rotor in each of the phases contains electrically conductive material; and the electrically conductive material of at least two phases is arranged and is interconnected in the rotor, such that if an alternating current flows through the stator windings of these phases, a current that generates a starting torque for the rotor is induced in the electrically conductive material. Advantageous modifications of the transverse flux machine according to the invention likewise are disclosed.
A starting torque can be obtained even without the permanent magnets, owing to the fact that the rotor in each of the phases contains electrically conductive material and that the electrically conductive material of at least two phases is arranged and interconnected in the rotor in such a way that a current generating a starting torque for the rotor is induced in the electrically conductive material if an alternating current flows through the stator coils of these phases. With the known transverse flux machine, a starting torque cannot be generated without the permanent magnets because of the single-phase state of the separately effective phases. In contrast, the machine according to the invention operates in such a way that the individual phases are magnetically independent, but electrically cooperate inside the rotor to form a magnetic rotating field machine. The aforementioned machine therefore behaves like an asynchronous transverse flux machine. By using an electrically conductive material with low specific resistance, the electrical losses in the rotor are relatively low, so that a satisfactory degree of effectiveness can be achieved.
The starting torque can preferably be obtained in that the stator coils of the individual phases can be admitted with currents that are phase-displaced relative to each other. In place of this or even in addition to this, the electrically connected rotor poles of the individual phases and/or the stator poles that are assigned to the electrically connected rotor poles of the individual phases can be geometrically displaced relative to each other. Given m phases, for example, the phases advantageously can be offset by an m-th part of double pole pitch. In that case, the currents and voltages flowing through the phases should also be displaced relative to each other in time by the corresponding angle.
If the electrically conductive material contained in the rotor forms a rotor cage with two short-circuit rings on the front, this cage corresponds to the standard rotor armature of an asynchronous machine.
The machine can be connected to a slip ring in place of a short-circuit ring if the machine is provided with a wire rotor winding, by way of which electrical power can be supplied from the outside. In that case, the machine displays a similar operational behavior as a known asynchronous machine with slip ring rotor. If the slip rings are supplied with direct current, the resulting machine behaves in the manner of an electrically excited synchronous machine.
The machine can be designed as unilateral or even as bilateral transverse flux machine. That is to say, the stator is located either on one side of the rotor only or on both sides of the rotor.
The machine can furthermore be designed such that it has either a rotating rotor or a rotor moving in linear direction.
In the following, the invention is explained in further detail with the aid of the exemplary embodiments shown in the Figures.